To understand the mechanism of carcinogenicity and organotropism of the ortho methyl aryl amines 3,2'-dimethylaminobiphenyl and 3-methyl-2-naphthylamine, study of the metabolism of these carcinogens in vivo in rats, mice and hamsters will be continued. A series of experiments will be begun to compare the metabolic profiles of these compounds in vitro in subcellular preparations of target and non-target tissues of the above species and also to determine the conjugated and non-conjugated metabolites in colon organ cultures and primary hepatocyte cultures. Using labeled carcinogens the degree and persistence of binding to macromolecules will be correlated with organotropism. Bioassays of N-oxidized derivatives, such as the C-nitroso forms and also of the N-acetylated derivatives in rodents will be undertaken. Studies of structure-activity relationships involving systematic alterations in the position of the methyl group with respect to the amino group and progressive oxidations of both the methyl and amino groups will be continued.